Extending MacBook Pro display to two additional monitors

I see two potential issues.

One is that you might need to tell the Mac that you want to run the displays in extended desktop mode.

Extend or mirror your Mac desktop across multiple displays - Apple Support

Another is that you might be connecting both displays through a "plain" USB-C dock and/or through a dock that uses some sort of second-class workaround. To drive two displays from a hub or dock in a hardware-supported way, you would need to use a Thunderbolt hub or dock, connected to the MacBook Pro by a Thunderbolt cable.

A Thunderbolt connection has more data pathways than a regular USB-C (DisplayPort Alt Mode) one, and a Mac wants to see the wider pathway before it will send two video signals over one port. (Even when the displays that you're using have low enough resolution that the extra bandwidth isn't strictly needed.)

If you don't have, or want to use, a Thunderbolt dock, then you should be able to just connect each display – or display adapter – through a separate Mac host port.

Thunderbolt is a connection method, not a particular brand or model of dock.

Thunderbolt docks that support two displays vary in what kinds of connections they provide. Some provide a dedicated DisplayPort or HDMI port – and let you connect a USB-C (DP) display or adapter to their Thunderbolt daisy-chaining port. Some split a Thunderbolt chain into multiple chains – and let you connect USB-C (DP) displays or adapters to two of their downstream Thunderbolt ports. What adapters you might need would therefore depend on which particular dock you picked.

Some vendors of Thunderbolt docks who have been in the business of selling Thunderbolt products to Mac users for a long time are:

Other World Computing

SonnetTech

CalDIgit

You didn't indicate which MacBook Pro you have, but if it has a 16" screen (not a 15" one) and a Core i9, that would narrow it down to one candidate: the MacBook Pro (16-inch, 2019).

MacBook Pro (16-inch, 2019) - Technical Specifications - Apple Support

It has four USB-C (USB, DisplayPort, Thunderbolt) ports and "simultaneously supports full native resolution on the built-in display at millions of colors and:

• Up to two displays with 6016‑by‑3384 resolution at 60Hz at over a billion colors
• Up to four displays with 4096‑by‑2304 resolution at 60Hz at over a billion colors"

So driving two extra monitors is not a problem at all. If that's the MacBook Pro that you have, it could drive as many as four UHD 4K (3840x2160 pixel) monitors.

the Apple store used to carry the Belkin USB-C to Gigabit Ethernet adapter. Tthat device works well, and may still be available aftermarket.

in the Apple store, it has been replaced with a more-capable model that sill works at lower speeds as well:

Belkin USB-C to 2.5Gb Ethernet Adapter - Apple - US$29.95

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RC135AMT wrote:

Do you know if there is a Thunderbolt that would connect the LAN? Or maybe I have to plug in two hubs.

Many Thunderbolt docks have Ethernet ports. Typically they support Gigabit Ethernet; some support 2.5 Gigabit Ethernet or even 10 Gigabit Ethernet. It's probably harder to find a Thunderbolt dock WITHOUT an Ethernet port than to find a Thunderbolt dock with one.

If you have any old Fast Ethernet (100 Mb/s) gear at home, check to see if a dock's Ethernet port can run at that speed. Likewise, if you are looking at a dock with 2.5 Gigabit or 10 Gigabit Ethernet, but your router provides a 1 Gigabit connection to your computer, check to see if the dock's Ethernet port can run at 1 Gigabit speed.